The determination of volatiles in a given substance is a very routine determination made countless times every day in numerous industries. Such tests are run on literally thousands of items ranging from agricultural products such as tests which determine the percentage of moisture in corn, wheat, oats, tobacco and the like to textiles, foods, films, coatings, paints, etc. Numerous industrial products and processes require testing to determine the percentage of volatiles, whether such volatiles be water, solvents or other diluents. These tests include the determination of the solid materials in paints, varnishes, lacquers, paper products, agricultural products and the like. Practically all items which are sold on a weight basis and are likely to absorb or contain moisture require correction for such gain or loss such that a customer is not charged for water or other diluent which might be in the particular material being sold. In the same manner, numerous items require a certain specified moisture or volatile level to be suitable for further use and are sold in the trade as being within specified ranges. Thus, considerable time is expended in quality control processes and tests to obtain the proper or desired percentage of moisture or solvent in the substance being processed or sold.
In a like manner, numerous industrial processes require constant determinations of moisture or solvent level as the product is being processed or manufactured. Consequently, industry and the trade has expended considerable efforts in the control and calculation of moisture and volatile content.
Previously, tests for determining the percentage of volatiles was conducted by typical weigh-dry-weigh analysis. The sample to be tested would first be weighed by an operator and then placed on a hot plate or in a vacuum oven for a predetermined period of time, normally on the order of 30 minutes to 4 hours. The sample would then be cooled, reweighed and a calculation made to determine the percentage of volatiles removed from the sample.
Another method used is known as the Karl Fischer determination. This test involved the titration with a specified chemical reagent and a subsequent calculation of the amount of moisture present based on the titration.
Such methods are time consuming and require operator skill. The accuracy of the test is often directly related to the skill and care exercised by the operator. Further, while such tests are largely repetitious, an operator is substantially limited in the number of tests which can be performed in a given period. In many instances, such as in quality control work, the time required for a signal test, i.e. as much as 2 hours or more, greatly inhibits plant operations such that processing conditions are normally two or more hours ahead of the test results. This requires advanced interpretation of processing conditions and estimations as to when the product is within specifications. Also, oven drying tends to drive off other volatile materials in addition to water. Thus, accuracy is often poor due to loss of other substances from the long drying times required.
In applicants' parent application noted above, an apparatus and method were described whereby volatiles in a sample material could be determined in a matter of minutes by means of an apparatus which automatically weighed the sample, volatilized the moisture and polar solvent by means of microwave heating and automatically calculated the weight loss and percent volatiles. While this determination was made within a matter of a few minutes, it has now been discovered that even faster determinations can be made, thereby making the present invention more suitable for inline computer processing control and other instances where even more rapid analysis is required. The present invention does not require the complete drying of the sample but rather determines the drying curve and mathematically projects the result after only a few minutes of drying induction time.
It is therefore an object of the present invention to provide an apparatus and process which automatically and rapidly determines the percentage of moisture or volatiles in a given substance in a fraction of the time previously required.
It is a further object of the present invention to provide an apparatus which projects the final dry weight of the sample without actually attaining complete dryness.
It is yet another object of the present invention to provide an apparatus and process which eliminates the possibility of overdrying of a sample.
It is yet another object of the present invention to provide an apparatus and process which can project moisture loss without the removal of other polar solvents if the same is not desired.
It is still another object of the present invention to provide a method which can be utilized in inline processing, such as in computer controlled processes, which require volatility measurements.
A further object of the present invention is to provide a method which eliminates the need for operator skill in determining the amount of volatiles in substances, reduces or eliminates the chance of human error and reduces the testing time to minutes or seconds per sample tested.
These and other objects will become apparent to those skilled in the art from the description of the invention which follows.